Study on the Bearing Capacity of the Polyethylene Pipe–Cured-In-Place Pipe Liner Composite Structure under External Pressure

Abstract

Cured-in-place pipe (CIPP) technology is used to repair deformed municipal polyethylene (PE) pipes caused by design flaws, construction issues, or external loads. However, research on CIPP for PE pipes is limited, restricting its broader application. This research focuses on the mechanical response characteristics and failure modes of the composite PE pipe–CIPP liner structure under external loads. Using experimental setups involving comparative test groups with different diameters and wall thickness ratios (DR values, defined as the ratio of the pipe’s outer diameter to its wall thickness), this study evaluates the effects of the liner’s elastic modulus, the bonding effectiveness at the PE pipe–CIPP liner interface, and the initial ovality of the pipes on the load-bearing capacity. The experimental results reveal that CIPP liners substantially enhance the stiffness and load-bearing capacity of PE pipes, with improvements ranging from 200% to nearly 500% depending on the pipe’s DR value. A novel ring stiffness prediction model is also introduced and validated against the experimental data. This model provides a theoretical framework for understanding the complex interactions at the PE pipe–CIPP liner interface and aids in designing more resilient urban drainage systems.